As will be observed herein the temperature of the liquid output from the collector and the efficiency of the collector and storage means is greatly increased through the use of strategically positioned temperature operated valves which control flow through the collector and which enhance stratification in the storage system assisted by the use of velocity reducers.
With conventional systems the head load may utilize only a portion of the heat content of the stored liquid as it passes through. Returning this water of intermediate temperature low into the storage tank tends to destroy stratification. By introducing a temperature operated valve after the heat load we can insure all available heat energy is removed in one pass, and when this low temperature liquid is returned low into the tank it enhances stratification. By throttling the liquid flow through the collector under marginal conditions for solar collection such as morning, afternoon, cloudy, or cold weather, with a second valve it is possible to get a more usable temperature and when conditions improve, the restricting effect produced by the throttling valve is removed and full flow is permitted to improve the efficiency of collection. The use of a third valve permits liquid from the solar collector, which is above a predetermined temperature, to pass in one direction to an upper strata of liquid within the storage tank but directs such flow to a lower strata if the temperature is below such predetermined value.
The problems addressed herein have been treated in a variety of generally more complex and expensive ways by the prior art. For example, commercially available electrical controls such as Hawthorne Industries H-1510-A sense water temperature and vary the speed of the pump motor to achieve usable temperature. U.S. Pat. No. 3,931,806 illustrates the use of a plurality of tanks in order to increase the efficiency of storage through maximizing temperature levels of the stored liquid. U.S. Pat. No. 4,021,895 illustrates the use of different collectors which deliver liquid in respect to varying levels in a storage tank. U.S. Pat. No. 4,027,821 illustrates sensing incoming water and utilizing another sensor within the tank to selectively determine the point at which the liquid will be introduced into the tank. Such systems are complex and expensive and the present invention contemplates simplification of apparatus and improved efficiency through sensing the temperature of the incoming water only so as to determine the temperature, the amount and the point of introduction thereof into the tank.
It is further contemplated that storage means may be provided utilizing a low cost heat source such as a solar collector which is backed up as by a heater disposed to heat the liquid in an upper portion of the storage tank and operated by a reliable but more expensive source such as off-peak electric power. By normally utilizing the liquid in a strata just below the heater, efficiency is improved since the higher temperature and more expensive heated water will remain at the very top and not be used until the usable energy in solar heated water is exhausted. This is in contrast to the prior art, as for example, U.S. Pat. Nos. 4,037,785 and 4,055,055 wherein liquid is always withdrawn from the top of the storage tank which results in utilization of electrically heated water even when adequately heated solar heated water is available at a slightly lower temperature.